With the rapid development of electronic products, they are increasingly important in daily life. In order to meet the market demand in space-saving and portability, electronic devices are becoming increasingly lighter and thinner, which requires the sizes of various components of the electronic devices, especially the thickness of each component to become smaller and smaller. For example, as one of the standard equipped components of the electronic devices, camera modules have a development trend of becoming light and thin.
As the number of pixels increases, the internal chip area will increase accordingly, the driving resistors, the capacitors and others will increase accordingly, such that the package size of the module also increases. The existing mobile phone camera module package structure contradicts the demands for thin and miniaturized camera module in the mobile phone. Therefore, there is a need to develop a new and compact package process to meet the product development need.
The structure of a conventional chip on board (COB) manufactured and processed camera module is formed by assembling a rigid-flex board, a photosensitive chip, a microscope base, a motor drive, and a lens assembly. The electronic components are arranged on the surface layer of the circuit board, and the components do not overlap each other. Along with the requirement for high-pixel and ultra-thin modules, the imaging requirement for the camera module is also getting higher and higher. Thus, the assembly is more difficult and device specifications are higher. At the same time, as the pixels are getting higher, the chip area will increase accordingly, and the corresponding passive components such as the driving resistors and the capacitors also increase accordingly, that is, the size of the module also increase.
At present, portable electronic devices represented by smart phones and tablet computers are increasingly lighter and thinner, which requires the size of each component of a portable electronic device (especially the thickness of each component) to become smaller and smaller. For example, as one of the standard components of the portable electronic devices, camera modules have a development trend of becoming light and thin.
The existing mobile phone camera module package structure contradicts the demands on the thin-type and miniaturization of the camera module for the mobile phone. Therefore, it is necessary to invent a compact camera module and a new-type package process thereof to meet the needs of product development.
FIG. 1 in the accompanying drawings of the specification illustrates a camera module based on the existing technology, wherein the camera module includes a lens assembly 1, a motor 2, an optical filter 3, a base 4, at least one gold wire 5, a drive control assembly 6, a circuit board 7, a photosensitive chip 8, and at least one motor welding spot 9. The photosensitive chip 8 is attached to the top surface of the circuit board 7. The photosensitive chip 8 and the circuit board 7 are conducted by the gold wire 5 (e.g., copper wire) through wire bonding. The optical filter 3 is attached to the base 4 or the lens assembly 1. After the assembling of the camera module is completed, pins on the motor are welded to conductively connect the motor 2 to the circuit board 7, so that the circuit board 7 can energize the motor 2 and further control motion of the motor 2.
Although the camera module has been widely used in the current camera module field, it still has many drawbacks.
First, in the process of manufacturing the camera module, the camera module needs to be welded after its assembly is completed. The process is not only complex, there may also be many additional problems caused by this welding process. For example, the product qualification rate is likely to be affected by the quality of the completion of the welding. At the same time, this welded connection is not secure and can be easily damaged during use and maintenance.
Next, the circuit board 7 and the photosensitive chip 8 are conducted through the gold wire 5. The fastening of this connection cannot be easily guaranteed. In addition, the base 4 has to offer a large protection space so that the gold wire 5 can be firmly fastened. In other words, the size of the base 4 is relatively large. Accordingly, the size of the entire camera module is fairly large.
Next, using the conventional process, the external welded electrical connection between the motor and the base is more susceptible to the external environment. For example, dust may affect its connection effect and service life.
In addition, in order to have a good supporting effect, the base has to possess a large size and occupy a large space, thereby increasing the size of the entire camera module. If the size of the base is reduced for reducing the size of the camera module, the supporting effect of the base may be affected.
In addition, the circuit board of the conventional camera module is separately disposed at the bottom of the camera module, which is relatively far from the elements that require energy supply such as the motor and the photosensitive chip, which not only consumes more energy-conducting elements, such as wires, but also fails to provide an adequate and proper location design for the elements constituting the circuit in the entire circuit arrangement of the camera module as required. Thus, spaces occupied by the elements constituting the circuit is not properly reduced. That is, if the relative positions between the circuit board and other elements of the camera module are properly arranged, the spaces occupied by the necessary circuit elements of the camera module may be further reduced, thereby further reducing the size of the camera module. Certainly, the width or thickness of the camera module may also be selectively reduced according to the market demands.
The conventional mobile phone camera module package usually adopts the CSP or the COB process. The electronic components are arranged on the surface layer of the circuit board, and the components do not overlap each other. For protecting the chip area on the surface layer of the circuit board, the autofocus camera module often needs a bracket to protect the internal components and support the motor. As the pixels increase, the internal chip area will increase accordingly, the driving resistance, the capacitance and other devices will accordingly increase, such that the package size of the module will also increase.
As described above, the connection between the circuit board 7 and the photosensitive chip 8 and the connection between the motor 2 and the circuit board 7 both need to occupy certain space and are difficult to be properly protected. At the same time, the base 4 has a relatively large size and is in contact with the circuit board 7, the photosensitive chip 8 and the motor 2. However, because of the non-conductive property of the base 4, a conductible connection between the circuit board 7 and the motor 2 and between the circuit board 7 and the photosensitive chip 8 cannot be realized.
The conventional camera module chip line is conducted by mounting a gold ball or a gold wire on the chip pad to be conductively connected with the circuit board pad, which adds a gold wire connection, a gold ball mounting process station in the manufacturing process, and increases the production cost and the yield rate loss. With the high-pixel development of the camera module, the number of the pads of the photosensitive chip is also increasing, and the pad spacing is also getting smaller and smaller, increasing the production difficulty and the production cost.
In addition, there are two types of approaches for connecting substrates in the camera module to the devices in the existing technology, one is a crimped connection and the other is a plug-in connection. The plug-in connection generally adopts an approach by combining a connector plug and a connector receptacle, and the plug-in connection generally adopts an approach by thimble contacting using a pin and a gold finger on the bottom of the substrate. Regardless of which approach is adopted for the substrate of the camera module, there is a problem that the substrates can only be connected to each other in an up-down orientation. That is, a photosensitive chip is attached to the upper surface of the substrate, a device is connected to the lower surface of the substrate, however, the crimped connection and the plug-in connection cannot be performed at the same time. Therefore, the structure of the camera module in the existing technology cannot meet the requirement of connecting different devices.
Furthermore, with the increase of the pixels of the camera module in the existing technology, the area of the photosensitive chip inside the camera module will also increase accordingly. Since the components such as the driving resistors and the capacitors will also increase accordingly, the package size of the camera module is also increasing. However, in the existing technology, the device for packaging the camera module has higher and higher requirements for the size of the camera module. In the existing technology, it is increasingly required that the size of the camera module after packaging be as thin as possible, and the smaller the better. Therefore, there is a contradiction between the actual situation and the current demand.
In addition, in the conventional camera module assembly process, an integrated circuit (IC) or a chip is conducted with the PCB by wire bonding (W/B) between pads or by solder paste welding between pads, that is, a chip scale package (CSP), and both of the above two technologies have certain limitations. The wire bonding (W/B) process requires a process of binding wire of the mounted ball for each pad (Pad), which takes more man-hour, affects the production efficiency and increases the manufacturing cost. The chip size package (CSP) process requires the IC to perform a land grid array (LGA) package, which is a surface mounting process for an integrated circuit (IC), and characterized in that the pins are located on the socket instead on the IC, but relatively increase the height of the IC, and there will be a solder paste thickness of about 50 um between the pads during welding, causing the height of the overall module higher than the wire bonding (W/B) process module. The CSP process does not meet the development trend of being thin, light and sleek for a modern mobile terminal.